There are some articles I try hard to avoid writing. Politics, religion, the so-called benefits of UV filters and other things that get Fanboys riled up I avoid like the plague. So for two years, while people have asked over-and-over for me to write an article on how we clean lenses, I've politely refused. I've seen what happens to such discussions on forums -- it's an immediate call for all Fanboys to come tell everyone else they're an idiot because they don't use Eclipse, or do use Eclipse, or brush before blowing, or blow before brushing, or whatever.
But I've had over 100 requests now, so I'm finally going to cave in. Since I'll be mentioning and recommending some products by name, my usual disclosure applies: we use what we use because we like the product, sometimes a lot. Unlike 99.9% of the internet we don't get discounts, kick-backs, click-through fees, or sell any of the things recommended at a profit. I don't put any links to the products to make sure that's clear. You can find it all with a quick Google.
What this is:
Mostly it's proof that the old saying "Be careful what you ask for. You might get it." is true. This is going to be massive overkill for 98% of people who asked how we clean lenses. You certainly aren't going to go out and buy all the supplies to do this to your own lenses every day (well, except for a few of you that have major Lens OCD: you know who you are). But there will certainly be some things you'll want to try, and probably a few tools you don't know about.
On a busy day we clean about 500 lenses, on slow days maybe half of that. We clean to what for most of you would be an unreasonable standard - not just the front element but the entire lens. Over the years we've probably tried every cleaning method there is short of kerosene and a blowtorch and we've considered that once or twice. That doesn't make our way the right way. It just makes it a way that works well for us.
What we use:
I'll start with a photo of one of our cleaning stations so you get an idea of how over-the-top our cleaining methods are. You may want to just say never mind and move along now. Or if all you want to know about is how we clean front elements, skip down toward the end of the article.
Don't get me wrong, you don't need half of this stuff. A lot of it is useful to us only because we do so many cleanings a day, and some of it because some of our techs prefer one thing to another. But for completeness, here's what we have at each station, using the numbers in the picture to give you location:
1: Large yellow chamois, Zeiss individual lens cleaning cloths in box, and blue microfiber cloth.
We use the chamois for cleaning barrels and cases. We don't usually use microfiber cloths on front elements: you never know when there might be a piece of grit in them which could scratch the elements. We use fresh Pec Pads for that. But microfiber cloths are more absorbant and we will occasionally use a new, clean one on front elements.
2: Lint removing brush (red) and two size lint rollers above it (Sensor Loupe above that doesn't count in this article).
Used for cleaning bags and the inside of lens hoods (the ones that have a felt lining).
3: Giottos Rocket Blower. The one thing everyone should already own.
4: Cleaning solutions -- Eclipse, ROR, Purosol Lens Cleaner, Purosol Sport and Marine cleaner. Two canisters of premoistened electronic cleaning wipes behind them.
Purosol cleaners and electronic wipes are used for the outside of lenses, hoods, and caps. We occasionally, but not often use Eclipse or ROR on lens elements. ROR is especially good when there are oily deposits.
5: DataVac Electric Blower. The greatest invention ever made, but you probably don't need one.
We avoid canned air: it can have propellants or other liquids that can stain glass (and it's relatively expensive in quantity). The DataVac Electric blower is the only thing we know of that uses no propellants or lubricants plus it's EXTREMELY powerful. Many times greater airflow than canned air. We use the Rocket Blower for sensitive places like front elements, the DataVac is too powerful. But for about $50 it keeps us all from getting carpal tunnel syndrome from pumping the Rocket Blower all day.
6: 8 different sizes and types of Lens Pen. Notice the large rectangular LapTop LensPen just to the right of the chamois, just to the left of the "6". More on LensPens later.
7: Two toothbrushes and in the lower right corner Pec Pads.
Soft toothbrushes are the only way to get dust and grit out of the cracks and crevices of front lens caps (Canon caps are particularly prone to gather it). A toothbrush and Purosol cleaner does a wonderful job of cleaning the grooves of rubber zoom and focus rings. We use Pec Pads instead of microfiber cloths on front elements: we know a fresh Pec Pad doesn't have any grit on it. That's hard to say about a previously used microfiber cloth.
Our basic method is cleaning from outside in: Case or pouch, then outside of the lens, the caps, and finally glass. There's no sense cleaning the lens barrel and then putting it back in a dirty case, or cleaning the front element and then putting a dust filled lens cap back on it. Cases are the easy part, of course. Simply blowing them out with an electric blower or vacuuming them takes care of dust, and a lint brush or roller handles anything left over. Canvas type cases, in particular, look much better after a good vacuuming.
The Lens Body, Hoods, and Caps
Obviously cleaning this doesn't make the lens work a bit better, but it's nice to have a clean lens. And it's definitely worthwhile for a lens you plan on selling. The plastic and metal on the outside of the the lens barrel, hood, camera bodies, and caps are easily wiped clean with a chamois dampened with cleaning fluid. We generally use Purosol. It's not the strongest cleaner but it leaves no residue and doesn't seem to cause any adverse effects on the rubber zoom or focus rings, or plastic distance windows. Tough areas are spot cleaned with a premoistened electronic wipe or a bit of eclipse.
The inside of hard plastic hoods can be cleaned in the same manner, but lint rollers or brushes are the best way to get dust and dirt from the inside of felt-lined hoods, particularly supertelephoto hoods. The inside of clip-on front element caps get the dust blown out of course, but dust tends to hide in the nooks and crevices of many caps, and inside the spring loops of Canon caps in particular. Brushing with a dry toothbrush usually dislodges it so it can be blown away, or a toothbrush sprayed with cleaner used to get the tough dirt out.
This is what most of you want to know about. The key to front element cleaning is to avoid damage. Blowing is always done first. You can't scratch an element by blowing and most large particles can be blown off using a Rocket Blower. (Canned air or a DataVac is really too strong, and as mentioned earlier it's possible to get some residue on the element using canned air.) Brushing (we use the brushes on the LensPens) is always done second to dislodge any particles, followed by blowing again to remove any particles loosened up by the brush. If further cleaning is needed after blowing and brushing, that's fine, but blowing and brushing is always first.
Our next step revolves around LensPens. We like several things about them: no liquid residue, simple and easy to use, gets into the edge of the lens better than most other methods. And out of the office, they're small and easy to carry around. They come in a variety of types and sizes and we use a number of different ones. Smaller ones are perfect for camera viewfinders, angled edges are great for lenses with deep edge recesses like fisheyes, etc.
The key to using a Lenspen is that you charge it (put the cap all the way on and take it all the way off) with each use so that the tip gets more cleaning dust. Also after using the lens pen, you should go back to blowing and brushing: if you look carefully with an angled light, you'll see a little fine grain dust has been left after the Lenspen use.
The most important point, though, is to not overuse a Lenspen. Once the felt on the tip gets worn, the rubber underneath doesn't clean, and can leave marks if used with too much pressure. We get, at best, 100 cleanings from a Lenspen, but that varies by which brand we're using and how big the lenses are being cleaned.
Lenspens do a great job on routine dirt, streaks and grime, but they won't get more stubborn "stuck on" gunk off of the front element, and aren't great with oily residue either. A wet cleaner is required for this stuff. We use Zeiss disposable lens cloths -- individual sealed pouches with a lens paper moistened with cleaner inside. We like that these are single use. Like I said, we're more paranoid about a piece of grit on the cleaning cloth damaging the lens than anything else. They're also convenient to toss a couple in your camera bag. But Eclipse on a PecPad works just as well, and ROR is what we reach for when we see obvious oily residue on an element.
PecPads are single use, too, and we like that, but they aren't as absorbant as a cloth. When we've had to use a fair amount of wet cleaner, sometimes a microfiber cloth is used to wipe off the cleaner simply because it's easier to get the streaks off than PecPads are. You may have noticed a microfiber cloth on the desk in my first picture: that cloth wouldn't be used on a lens element, it would be for less critical things like LCD covers. Only a clean, been-kept-in-a-pouch microfiber cloth should touch a front element.
Many of you know we don't get freaked out about tiny front element scratches. We test to make sure they don't cause flare or contrast loss and otherwise don't worry with them, they won't do anything else. But a lot of people, including perhaps the future buyer of your used lens, will care a lot, so it's worth trying to keep the element as pristine as you can.
Cleaning rear elements is certainly more important from an image quality stand point than front elements, but since rear elements aren't exposed to the environment it's rarely necessary to do more than blow off dust. Many lenses are "rear focusing" so before cleaning the rear element turn the focus ring to bring the element up to the surface of the lens.
If more than blowing and brushing is required, be careful to keep your fingers away from the electrical contacts on the lens when cleaning. Just a bit of skin oil on the contacts can interfere with electrical signals transmitting between camera and lens. If you do find an ERR message after cleaning a lens, you can lightly rub a clean pencil eraser over the contacts to remove the oil. There are people online who give longwinded warnings about this eroding contact metal, and it might if you do it every day, but every factory repair service we know of uses that technique, so we do to.
Is All This Necessary?
Absolutely not. Those of you who wear glasses just take them off and look at them. They can be fairly filthy and not interfere with your vision. The front element of your lens can also be fairly filthy and not affect image quality at all. If you don't believe me go put a a couple of 1/4 inch wide piece of post-it note on your front element and take some pictures. You won't be able to tell it was there, any more than you can tell a fair amount of dust is there. Or look at our example or Kurt Munger's. That being said, very wide angle lenses at small apertures may be the one exception to the rule: the depth of field in that case may come close to bringing front element dirt or scratches into the plane of focus. Maybe.
Oily films or haze or thick coatings of dust can definitely affect image quality, though, and probably should be cleaned as soon as possible. However, lots of small scratches can affect contrast and deep scratches can cause lens flare, so the key is to keep your lenses reasonably clean but avoid putting multiple cleaning scratches on the front element. So we believe blower, brush, and meticulously clean (read single use) cloths for cleaning are the key.
But that's just our opinion. We know breathing on the lens and using the corner of your T-shirt usually works. Almost any cleaning method usually works and has it's advocates. Just letting the lens be incredibly dirty usually works, too. But most of us (and as best I can tell all of our customers) like their gear to look as good as it did when they first got it, and these are the methods we use to do that.
A note on comments
With a bit of hesitation, I'm leaving the comments section open in this article. Thoughtful comments, questions, and suggestions are welcome. What I've written above is the way we've performed some 120,000 cleanings, but that doesn't mean I know it's the right way. The only thing I know for certain about cleaning lenses is that sandpaper and chisels should be used, at most, sparingly. Everything else is open for discussion.
But this isn't a forum, it's our clubhouse, and we don't find the "anyone who doesn't do it my way is an idiot" type of comment acceptable. There are already plenty of forum threads about cleaning lenses that are full of those posts, there's no need for more. Of course, anything that hints of "selling a product", even the ones we've recommended, in the comments will be deleted immediately. Our readers are big boys and girls, they know how to use Google to find what they want.